DE2624349C3 - Process for the production of hexafluoroacetone - Google Patents

Description

The invention relates to a process for the production of hexafluoroacetone from hexafluoropropene.

In particular, the invention relates to a process for the preparation of hexafluoroacetone from hexafluoropropene with high performance and using a special catalyst.

As such, hexafluoroacetone is used as a catalyst for the polymerization of perfluorocyclobutene or triazine applicable. Due to its polymerisability, it forms a terpolymer with tetrafluoroethylene and ethylene. This compound is also used as a starting material for the manufacture of bisphenol AF

[(C ₆ H ₄ -OH) ₂ C (CFj) ₂ ]

suitable which is an excellent crosslinking agent for fluorine-containing elastomers

For the production of hexafluoroacetone, a process is already known in which hexafluoropropene is used oxidized and the resulting 1,2-epoxyhexafluoropropane subjected to a rearrangement to hexafluoroacetone So z. B. Hexafluoropropene and oxygen with activated silica gel at temperatures from 140 to Brought into contact with each other at 280 ° C., thereby obtaining 1,2-epoxyhexafluoropropane. This compound is in the presence of a Lewis acid, e.g. B. Alumina rearranged to hexafluoroacetone (US Pat. No. 3,775,439). Thus, in the conventional The process requires two reaction stages in order to arrive at the desired hexafluoroacetone.

It has now been found that hexafluoroacetone from hexafluoropropene and oxygen by a one-step Process can be produced if the reaction is carried out on a special fluorinated aluminum oxide

The invention therefore relates to a process for the preparation of hexafluoroacetone from hexafluoropropene, which is characterized in that you hexafluoropropene and oxygen with a fluorinated aluminum oxide, which in the usual way by reaction of activated alumina with a fluorinating agent at a temperature of 80 contacted up to 300 ° C

The invention makes it possible in a technically advanced manner, hexafluoroacetone in one one-step process from hexafluoropropene and oxygen. It must be surprising be considered to be the intermediate occurring in the above-mentioned two-step process 1,2-Epoxyhexafluoropropane not detected when carrying out the method according to the invention can be. In the conventional method, the second stage reaction is usually carried out in the presence carried out a Lewis acid as a catalyst.

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While the conventionally used, known oxidation catalysts (z. R silicon dioxide) for hexafluoropropene mainly 1,2-epoxyhexafluoropropane generate, it is found that the invention in On the other hand, practicing fluorinated alumina under consideration does not form 1,2-epoxyhexafluoropropane Lewis acids (e.g. aluminum oxide, Ahiminium trichloride), which are used as catalysts for the rearrangement of 1,2-Epoxyhexafluoropropane to hexafluoroacetone are known in the reaction of hexafluoropropene with Oxygen does not show any activity. From these facts, it can be presumed that the fluorinated alumina contributes to the selective formation of HexafluoraceUMi the oxidation of hexafluoropropene results

Fluorinated aluminas are used in the process of the present invention, some of which already as catalysts for reforming hydrocarbons and others as catalysts for the rearrangement of chlorofluorocarbons are known. Although with the invention Process any catalyst obtained by reacting activated alumina with a Fluorination agent is used can be, the use of such fluorinated aluminum oxides is expedient as im essentially contain aluminum, fluorine and oxygen and their fluorine content is approximately 0.5 to 50% by weight

The fluorinated alumina used as a catalyst is conventionally by treating activated alumina with a fluorine ring agent

As activated aluminum oxide, all conventional products, e.g. B. natural alumina or synthetic alumina may be used, e.g. B. highly porous aluminum oxide, obtained by calcining α-aluminum oxide hydrate or 0-aluminum oxide hydrate under appropriately controlled conditions. Some, in trade Available activated alumina types contain silica as a component for tablet formation. The presence of silicon dioxide or Silica in amounts up to about 20% by weight based on the total amount in the alumina itself practical for the preparation of the catalyst that is used in the method according to the invention is to be used, not disadvantageous. However, if the proportion is more than about 50% by weight, then the catalytic The activity of the catalyst is extremely reduced, making industrial use impossible.

Inorganic fluorination agents or organic fluorination agents can be used as fluorination agents. Examples of inorganic fluorinating agents are hydrogen fluoride, silicon tetrafluoride, sulfur fluoride (e.g. sulfur tetrafluoride, sulfur hexafluoride), sulfuryl fluoride, thionyl fluoride, ammonium fluoride (e.g. acidic ammonium fluoride, neutral ammonium fluoride, hydrobromide hydrocarbons, hydrochlorofluorocarbons, hydrocarbons, etc.). Fluorine-containing compounds of the formula CF ₁ HaX, in which X is an oxygen atom or a nitrogen atom, η is an integer from 1 to 8 (preferably 1 to 4), a is an integer from 1 to 2n + m , b is an integer from 0 to 2 / i + m-1 and m is an integer of 2 when X is an oxygen atom or an integer of 3 when X is a nitrogen atom as described in the published documents of Japanese Patent Application 1578/1972.

can also be used as organic fluorinating agents. The fluorocarbons Saturated or unsaturated hydrocarbons with no more than 8, preferably no more than 4 Be carbon atoms in which at least one hydrogen atom is substituted by a fluorine atom However, a higher degree of substitution with fluorine atoms is more preferred. Specific examples thereof are given the following substances:

CF ₄ , CHF ₃ , CF ₃ CF ₃ , CHF ₂ CF ₃ ,

CHF ₂ CHF ₂ , CH ₃ CFj, CH ₂ FCHF ₂ , CH ₂ = CF ₂ , CF ₃ CF = CF ₂ , CF ₂ = CF ₂ etc.

The chlorofluorocarbons and the bromofluorocarbons can be saturated or unsaturated Be hydrocarbons with not more than 8, preferably not more than 4 carbon atoms, in which Hydrogen atoms are substituted by at least one fluorine atom and at least one chlorine or bromine atom. Individual examples of this are the following substances:

CCL ₃ F, CCl ₂ F ₂ , CHCl ₂ F, CHClF ₂ , CClF ₂ CCl ₂ F, CCl ₃ CF ₃ , CCl ₂ FCCI ₂ F, CCl ₃ CCl ₂ F, CClF ₂ CClF ₂ , CCI ₂ FCF ₃ , CF ₃ CCI = CCICF ₃ , CF ₂ BrCFClBr, 2-,

CF ₂ BrCHCIF, CF ₂ BrCF ₂ Br etc.

Examples for fluorine-containing compounds are hexafluoroacetone, hexafluoro-l, 2-epoxyäthan, Decafluordiäthyläther, tri (tri-fluormethyO-amine, Tetrafluoräthyl-me- m thyläther etc. Among them, perfluoroalkanes, z. B. fetrafluormethan, and perfluoroalkenes, z. B. hexafluoropropene, particularly preferred

The preparation of the catalyst can vary according to the type of fluorinating agent used which procedures are going on.

If z. B. hydrogen fluoride or ammonium fluoride is used as the fluorinating agent, then the activated aluminum oxide is ^{brought into contact with it at temperatures of about 20 to 450 °} C., so that the fluorinated aluminum oxide is obtained.

If sulfur fluoride, sulfuryl fluoride or thionyl fluoride is used, then the activated Aluminum oxide brought into contact with the fluorinating agent at temperatures of about 300 to 500 ° C 4-, to obtain the fluorinated alumina. In some cases, sulfur-containing compounds can be used are formed and deposited on the catalyst. However, these are not responsible for catalytic activity harmful. w

When the fluorinating agent is an organic fluorinating agent, then the activated alumina can thus at a temperature of about 100 to 600 ° C, are preferably brought from about 150 to 450 ⁰ C, in contact to provide the desired fluorinated γ to produce alumina.

In the case of the use of an organic fluorinating agent, the treatment of the activated Alumina with a chlorohydrocarbon or a bromohydrocarbon before contact t, o be carried out with the organic fluorinating agent. The coexistence of a chlorinated hydrocarbon or a bromocarbon in the Contact of the activated alumina with the organic fluorinating agent is μ in some cases Recommended because the fluorination of activated alumina is smoother at lower temperature can be done.

As chlorinated hydrocarbons or bromine hydrocarbons, saturated or unsaturated hydrocarbons with not more than 8, preferably not more than 4 carbon atoms in which at least one Hydrogen atom is substituted by a chlorine or bromine atom, can be used. A higher degree of substitution with chlorine or bromine atoms becomes more preferred Substitution with chlorine or bromine atoms alone or with both is permissible. Specific Examples are the following substances:

CCU, CHCl ₃ , CCl ₃ CCI ₃ , CHCl ₂ CCl ₃ , CCI ₂ = CCl ₂ , CHCl = CCl ₂ , CHBr ₃ , CCI ₂ Br ₂ etc.

Among these compounds, perchlorohydrocarbons are particularly preferred

When producing the fluorinated aluminum oxide by treating the activated aluminum oxide with the fluorocarbon and the chlorinated hydrocarbon or the bromocarbon, the activated aluminum oxide can first be mixed with the chlorinated hydrocarbon or with the bromocarbon at temperatures of about 100 to 400 ^° C. (preferably 100 to 200 ^° C.) and then treated with the fluorocarbon at temperatures of about 100 to 400 ⁰ C (preferably 100 to 350 ° C) are contacted, thereby fluorinated alumina can be obtained.

Alternatively, the activated alumina can also be mixed with the chlorinated hydrocarbon or the bromocarbon and the Contact fluorocarbon at temperatures of about 100 to 400 ° C (preferably 200 to 300 "C). The mixing ratio chlorinated hydrocarbon or Bromocarbon to the fluorocarbon is determined by the respective type. B. a combination of carbon tetrachloride and trichlorotrifluoroethane is used then the molar ratio from carbon tetrachloride to trichlorotrifluoroethane expediently about 0.1 to 5: 1.

In addition to the procedures described above, the fluorinated alumina can be used in any of the following ways any conventional method, e.g. B. according to the procedures described in Japanese Patents 11605/1964 and 27 748/1968 are described.

If the catalyst is used for a period of time, carbonaceous materials will be deposited on its surface, thereby reducing the catalytic activity. In such a case, the catalytic activity can be regained by treating the catalyst in the presence of oxygen or an oxygen-containing material, e.g. B. heated air at temperatures of about 350 to 500 ⁰ C.

The inventive method can be carried out in such a way that one hexafluoropropene and Oxygen contacted with the fluorinated alumina catalyst in a conventional manner. Consequently can e.g. B. the hexafluoropropene and the oxygen in a fixed bed, a moving bed or in one Fluidized bed of the catalyst in a suitable reaction vessel or tube and in a continuous system or in a closed system be brought into contact with each other.

The mixing ratio of hexafluoropropene to oxygen is usually about 1:10 to 0.1 (molar ratio), preferably about 1: 2 to 0.3. If the

If the amount of oxygen is below the lower limit of this range, then the conversion rate is only low. On the other hand, if the amount of oxygen is above the upper limit, then the Performance of the device reduced. If necessary, an inactive gas, e.g. B. carbon dioxide, nitrogen or helium, as a diluent be used.

The reaction temperature on contact is usually about 80 to 300 ° C, preferably about 100 to 250 ° C. If the temperature is below the lower limit of this range, the conversion rate will be lowered. On the other hand, if the temperature is above the upper limit, the yield will be reduced at temperatures below about 80 ° C, the reaction hardly proceeds at temperatures above about 300 ⁰ C, the yield is extremely low. The reaction pressure can be atmospheric pressure or a higher pressure. In general, a higher pressure is preferable to increase the conversion efficiency and the yield. For the technical implementation, a pressure of about 0.98-20.6 bar is usually used

The contact time is determined by the other conditions, in particular the temperature. A shorter contact time is selected at a higher temperature, while a longer contact time is selected at a lower temperature Contact time is appropriate, as is the case with other common reactions. In general, one is Contact time of 30 minutes or less (e.g. 0.5 seconds) is preferred. A longer contact time results to a higher conversion. In individual cases, the correct contact time may be due to economic considerations elected out. A contact time of about 1 second to 10 minutes is usually required continuous systems used in which the temperature is around 100 to 250 ° C

The examples illustrate the invention.

example 1 (1) Preparation of the catalyst

In a reaction tube made of Pyrex glass (diameter

28 mm, length 1000 mm) in an electric furnace is arranged vertically, granular activated alumina with a particle size of 23 to 4.7 mm (alumina gel) (51.25 g) was added. The dehydration takes place by single heating

in 500 ⁰ C in a stream of nitrogen. The temperature is then lowered to 200 ° C. The supply of nitrogen is stopped and a mixed solution of CCU and CF ₂ ClCFCl ₂ (molar ratio 1: 1) is discharged from the top of the at a rate of 1 g / min Reaction tube inserted. The upper part of the alumina layer immediately showed a rise in temperature up to 270 ° C. The zone of high temperature gradually moves towards the lower layer, and after 40 An equilibrium has been reached in which the minutes entire aluminum oxide layer shows a temperature which is about 10 ⁰ C higher than the planned temperature. The planned temperature is then increased to 250 ^° C. In this case too, a small, hot spot is produced, which becomes the lower layer in the Course of the treatment time agitated After 45 minutes it runs through the bottom layer. the The planned temperature is increased to 300 ° C, which means that there is hardly any increase in temperature. To 40 minutes of treatment will cool the oven

jo left and the catalyst is removed.

The catalyst thus obtained has a Fluorine content of 93% by weight and is used as a »catalyst I « In the same way, the following

j) conditions other catalysts produced as "Catalyst II" and "Catalyst III" are designated.

catalyst

CCI ₄ ZCF ₃ -CICFCi ₂

(Molar ratio)

Flow velocity the mixed solution

(g / min)

Working time (h) 200 ⁰ C 25O ° C

300 ⁰ C

Fluorine switch

(Weight%)

Il III

0.1: 1 0: 1

1.0 1.0

(2) Production of hexafluoroacetone

The catalyst I obtained in (1) (50 g) (apparent volume 50 ml) is introduced into a reaction tube made of Hastelloy-C, which has an internal diameter of 18 mm and a length of 1 m : 0.7) is introduced under the following conditions: temperature 170 ^° C.; Pressure 5.9 bar; Amount of gas supplied 100 ml / min (25 ° C, pressure 0.99 bar).

That discharged from the reaction tube 3 hours after the start of the introduction of the gas mixture Product gas is gas chromatographed and examined by infrared spectroscopy and mass spectroscopy. The following results are obtained:

link

Mol%

CF ₃ CF = CF ₂

CF ₄

CO ₂

65.6 7.3 1.5

0.5 I.

0.7 I.

0.6 0.83

9.1 9.3

link

CF ₃ COF

CF ₃ COCF ₃

CF ₃ CFCF ₂

Mol%

3.1

15.9

B e i s ρ i e 1 e 2 to 11 and Comparative Examples 1 to 5

Hexafluoropropene and oxygen are used with the bo catalyst in the same way as in Example 1 (2) at the conditions shown in Table I. The catalyst used is the same as in Example 1 (1) had been prepared. The composition of the 3 hours after the start of the introduction of the Gas mixture discharged gas is determined by gas chromatography. Infrared spectroscopy and mass spectroscopy examined the results obtained are compiled in Table I.

7th 26th 24 349 8th Material of Reaklinns- Table I. Reaction total quantity pipe tcmpcriilur Reactionary HHVO, *) of the current pressure Gas CC) (ml / min) **) (bar) (Molvcrhällnis) Pyrcx glass Rrfindiingsgcm. Pyrex glass Examples 215 120 Pyrex glass 2 ! Ή) 0.99 1.4 100 'Pyrcx glass 3 220 0.99 2.3 260 Pyrex glass 4th 200 0.99 0.8 120 Hastelloy-C 5 250 0.99 1.4 140 Hastelloy-C 6th 185 0.99 1.0 60 Hastelloy-C 7th 145 4.41 0.9 40 Hastelloy-C 8th 150 4.32 0.9 40 Hastelloy-C 9 170 4.51 1.8 60 IO 170 5.40 1.8 60 11th 4.91 1.8 Pyrex glass Comparative Hastclloy-C examples 270 100 Pyrex glass 1 290 0.99 1.0 100 Pyrex glass 2 200 0.99 1.0 120 Pyrcx glass 3 200 0.99 1.4 120 4th 170 0.99 1.4 120 5 0.99 1.4

*) HFP = Hcxafluorpropcn.
**) 25 ° C, 0.99 bar.

Table I (continuation)

catalyst lot Composition of CF ₄ discharged gas (mol%) COF ₂ there is no reaction CF ₃ COF CF ₃ COCF ₃ CF ₃ CFCF ₂
O Art (ml) CF ₁ CF = CF ₂ CO, Invention 0 appropriately
example 50 12.3 6.0 0.4 12.3 0 2 II 50 66.6 6.0 2.0 3.1 0.3 7.6 0 3 II 50 82.0 9.3 1.3 4.6 0.5 4.0 0 4th III 50 80.1 20.2 1.5 9.7 0.1 13.4 0 5 I. 50 53.4 22.5 3.2 9.9 0.5 10.3 0 6th I. 30th 51.5 14.1 3.3 11.6 4.1 16.5 0 7th II 30th 49.8 9.3 3.9 8.2 3.3 18.0 0 8th I. 30th 58.5 6.0 2.7 5.8 4.3 11.1 0 9 III 30th 70.8 7.2 2.0 6.0 3.0 15.9 0 10 I. 30th 65.9 7.8 2.0 6.1 2.9 13.7 11th I. 67.4 2.1 5.7 Comp.-
example 0 0 23.2 23.2 0 5.9 1 - 0 40.2 0 7.7 23.2 32.9 2.2 0 2 - 50 27.9 0 7.8 0 0 0 3 AI ₃ Q ₃ -GeI 50 99.8 0.2 4th AIF ₃ 50 5 AICh

Example 12

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2.0 g of the catalyst II obtained in Example 1 ('.} Are introduced into a 17 ml stainless steel autoclave, and the temperature is kept at 130 ^° C. A mixture of hexafluoro-

Table Il

propene and oxygen (molar ratio 1: 1) introduced until the pressure is 4.91 bar. The composition of the Gas in the autoclave contents is gas chromatographed 10 minutes and 1 hour after the start of the reaction certainly. The results obtained are summarized in Table II.

Composition of the gas (mol%) ChCK-CF ₂ CF ₄ CO ₂

COK,

CK ₁ COl '

CK ₁ COCK

To K) min 51.2 13th 13.3 3.7 To I ii 38.2 17.0 4.7 example

11.1
14.2

Table ill

(1) Preparation of the catalyst

(A) In a reaction tube made of Pyrex glass (diameter 28 mm, length 1000 mm) placed vertically in an electric furnace, 50 g of granular activated alumina as used in Example 1 (1) is placed. While hexafluoropropene is introduced into the reaction tube, the temperature is increased to 200 ⁰ C. The formation of carbon monoxide and carbon dioxide at 160 ^° C. is determined. The temperature is ^{kept at 200 °} C. for 1 hour. During this time, hexafluoropropene is allowed to flow in at a rate of 80 ml / min (25 ° C.; 0.99 bar). The temperature is then increased to 250 ^° C. and the temperature is held there for a further hour. During this time, hexafluoropropene is introduced in the same amount as above. The temperature is increased further to 450 ° C in a stream of nitrogen, whereupon oxygen at a rate of 100 ml / min (25 ° C, 0.99 bar) over a period of 1, 5 hours is passed through. The fluorinated aluminum oxide obtained in this way as a catalyst has a fluorine content of 4.02% by weight.

(B) as in (A) 50 g of granular activated alumina are introduced into a reaction tube, and the temperature is raised in a nitrogen stream to 200 ⁰ C. While maintaining this temperature hexafluoropropene is for 40 minutes at a rate of 80 ml / min (25 ° C; bar 0.99) passed The temperature is raised in a nitrogen stream to 450 ⁰ C, and then oxygen at a rate of 100 ml / min (25 ° C., 0.99 bar) passed through for 14 hours. The fluorinated aluminum oxide obtained in this way has a fluorine content of 130% by weight.

(C) as in (A) 50 g of granular activated alumina are introduced into a reaction tube, and the temperature is raised in a nitrogen stream at 350-370 ⁰ C. While this temperature is maintained, sulfur hexafluoride is introduced into the reaction tube at a rate of 200 ml / min (25 ° C., 0.99 bar) over the period of time given in Table III. In this way the respective fluorinated aluminum oxide is obtained with the fluorine content given in Table III.

4.1
4.7

16.6
21.2

Clued
Alumina no.

Uchandlungszcil
(H)

Kluoi salary
(Weight%)

(D) 50 g of granular activated aluminum oxide with a particle size of 2.3 to 4.7 mm are introduced into a reaction tube made of Hastelloy-C (18 mm diameter, length 1000 mm), which is arranged vertically in an electric furnace. The temperature is raised in a nitrogen stream to 120 ⁰ C, and hydrogen fluoride is 4 hours at a rate of 100 ml / min (25 ⁰ C; 0.99 bar) was introduced at 120 ° C. ^{The temperature is then increased to 420 °} C. in the nitrogen stream, and this temperature is maintained for 3 hours in order to eliminate water and hydrogen fluoride. In this way, fluorinated alumina having a fluorine content of 30% by weight is obtained.

(E) Place in a 200 ml stainless steel autoclave 50 g granular activated aluminum oxide with a particle size of 2.3 to 4.7 mm (aluminum oxide gel) and then a vacuum is applied.

1 g of hydrogen fluoride is introduced into the autoclave, whereby the generation of heat is observed. After 40 minutes, the temperature is ^{increased to 100 °} C. for 1 hour and then to 420 ^° C. The contents of the autoclave are kept at this temperature under a pressure of 0.99 bar for 3 hours, whereby water and hydrogen fluoride are eliminated. The fluorinated alumina obtained in this way had a fluorine content of 2.63% by weight.

(F) As in (D), granular activated alumina is mixed with gaseous hydrogen fluoride a rate of 200 ml / min (25 ° C, 0.99 bar) 4 Treated at 140 ° C for hours. This becomes fluorinated Obtained aluminum oxide with a soil content of 49.8% by weight.

(G) 50 g of granular activated aluminum oxide as in (D) are immersed in a 20% strength aqueous solution for 30 minutes

C, 0.5 0.5 l C ₂ 1.8 2.5 i C ₁ 2.5 3.5 C ₄ 5 5.5 ! C, 9 12.3

Immersed ammonium fluoride solution. The activated alumina is made from the ammonium fluoride solution taken out, dried at room temperature under reduced brück and then placed in a reaction tube introduced from Hastelloy-C. The reaction tube is heated to 550 ° C. for 5 hours. During this time nitrogen is passed through. The fluorinated alumina obtained has a fluorine content of 4.5% by weight.

(H) As in (D), 40 g of granular activated aluminum oxide are mixed with sulfuryl fluoride (300 ml / h; at 25 ° C, 0.99 bar) treated at 427 ° C. for 3 hours. In this way, fluorinated alumina becomes with a Obtained fluorine content of 1.5% by weight.

(2) Production of hexafluoroacetone

40 g of the catalyst obtained in (1) are introduced into a reaction tube made of Hastelloy-C with an internal diameter of 18 mm and a length of 1 m. A mixture of hexafluoropropene and oxygen (molar ratio 1: 1) is introduced under the following conditions: temperature 175 ^° C.; Pressure 1 at; Amount of gas supplied 80 ml / min (25 ° C, 0.99 bar). The composition of the discharged gas is examined by chromatography. The results obtained are shown in Table IV.

Table IV *) Thoroughly Fluorine content
(Wt .-%)
at the start d. Catalyst
after 50 ii composition
CF ₄ CO, 1.5 of the discharged gas
COF ₂ CF ₁ COF 3.0 (Mol%)
CIiCi = CF ₂ CF ₁ COCF-, Fluorinated
aluminum
oxide no. *) 1.50 8.22 5.0 1.5 4.4 3.0 74.2 11.9 Il 2.50 8.13 5.3 1.7 4.2 3.0 73.7 12.3 C ₂ 2.63 8.20 5.2 2.8 4.0 3.5 74.4 11.7 E. 4.50 7.90 4.4 1.8 4.5 3.8 72.8 12.U G 4.02 8.12 5.2 1.0 4.2 3.8 72.7 12.3 A. 12.3 12.4 5.5 0.4 3.8 2.5 73.4 12.5 C ₅ 30.0 30.0 2.1 0.1 2.6 0.1 87.6 4.8 D. 49.8 49.8 0.5 rlahrensweise. 0.3 98.2 0.8 F. of the Ve described above llt_ _._ ll ___. Example 14

(1) Preparation of the catalyst

50 g of granular activated aluminum oxide according to Example 1 (1) are placed in a reaction tube made of Hastelloy-C (inner diameter 18 mm, length 1000 mm), which is arranged vertically in an electric furnace. The dehydration takes place for 2 hours at 450 ° C in the nitrogen atom, after which the temperature is lowered to 170 ° C. The nitrogen feed is interrupted and a mixture of C ₂ F _b and O ₂ (molar ratio 1: 1) is fed in at a rate of 80 ml / min (25 ° C., 1 atm) from the top of the reaction tube. The temperature of the aluminum oxide layer shows a temporary increase and falls to 170 ° C. after 30 minutes. At this temperature, the introduction of this mixture is continued for 1.5 hours. During this time, the formation of _{trace amounts of CO 2 is} detected. The temperature is then increased to 200 ° C and the mixture setting is continued for 4 hours. During this time, the formation of a small amount of CO 2 is detected , and the formation of CF ₃ COCF ₃ and CF4 is observed with an increase in the amount of CO ₂ formed. The internal temperature reaches 220 ° C. in 2 hours. The reaction tube is allowed to cool by bubbling nitrogen through it, and the catalyst is taken out. The fluorine content of the catalyst obtained in this way is 1.8% by weight. A deposition of a carbonaceous material is not detected

40 g of the catalyst obtained in (1) are placed in a reaction tube made of Hasteüoy-C with an internal diameter of 18 mm and a length of 1 m and the temperature is increased to 160 ° C. Hexafluoropropene and oxygen are fed into the reaction tube in amounts of 30 ml / min and 20 ml / min (25 ° C, 0.99 bar) introduced, whereby the internal temperature rises rapidly to 190 ° C and an equilibrium at this Temperature is obtained. The composition of the taken from the reaction tube at this point in time Gas mixture is as follows:

1.2 mole percent CF ₄ ; 10.5 mole percent CO ₂ ;

2.1 mole percent CF ₃ COCF ₃ , 86.2 mole percent C ₃ F ₆ .

Then the internal temperature is gradually lowered, and it reaches about 15 hours after the start of the Introduction of hexafluoropropene and oxygen a constant temperature of 177 ° C. At this time shows the gas mixture withdrawn from the reaction tube the following composition:

4.8 mole percent CF ₄ ; 1.1 mole percent CO ₂ ;

3.8 mole percent COF ₂ ; 1.2 mole percent CF ₃ COF;

133 mole percent CF ₃ COCF ₃ ; 75.8 mole percent C ₃ F ₆ .

The supply of hexafluoropropene and oxygen is continued until 30 hours have passed from the start. During this time, the proportion of CF ₄ , COF ₂ and CF ₃ COCF _{3 increases} somewhat, while the proportions of CO ₂ and CF ₃ COF taper off

13 14

Have weight loss. The fluorine content of the 40 ml / min or 20 ml / min (25 ° C, 0.99 bar) below a Reaction tube out after the reaction has ended - overpressure of 3.9 bar introduced. Has after 20 hours taken catalyst is 8.30 wt .-%. the gas taken out of the reaction tube

. , mix the following composition:

Example 15 _r

0.5 mole percent CO; 1.5MoI-OZoCF ₄ ;

In a reaction tube made of Hastelloy-C, 40 g of the ...., “/ r-n non * ι η / # -vm?

Catalyst C ₄ entered, and the temperature becomes' · ° ^{Mo |} - ^{% C} ° ^{2: 12} x ^{0 Mo} '- ^{% COFj;}

at 15O ⁰ C increase in nitrogen flow. Then 12.3 mole percent CF ₃ COF; 26.2 mol%

and O? into the reaction tube in amounts of CF ₃ COCFi; 46.5 mole percent C ₃ Fe.

Claims (1)

Claim: Process for the production of hexafluoroacetone from hexafluoropropene and oxygen, thereby characterized in that one hexafluoropropene and oxygen with a fluorinated aluminum oxide, which has been prepared in the usual way by reacting activated aluminum oxide with a fluorine at one temperature contacted from 80 to 300 ° C